This description relates to controlling the charging of a battery and maintaining a full charge capacity of the battery by lowering a cut-off current.
A typical portable computing device, such as a notebook computer or a portable digital assistant (PDA), is supplied with a common alternating current using an adaptor, or with power using a battery. Since the typical portable device is frequently carried by a user, the weight and the size of the device and its components, such as the battery, are important.
The battery typically used in the portable device is a rechargeable secondary battery. A secondary battery having a higher energy density is preferred due to the relative compactness and reduced weight of the battery.
One type of secondary battery utilized is a secondary lithium-ion battery that is environmentally less intrusive and relatively light and compact. The lithium-ion battery generally has a long lifespan, conserves energy well, has a high energy density, and has a high operational voltage. Accordingly, the secondary lithium-ion battery is used for portable devices such as personal computers, camcorders, portable phones, CD players, and PDAs.
One type of charging technique for a battery includes applying a preset charging scheme regardless of a design capacity of the battery. For example, a charging scheme for a battery is determined without respect to the design capacity of the battery, and the battery is typically charged according to the predetermined scheme. Accordingly, the charge for the battery is adjusted by compensating for a charge voltage and a charge current for the battery based on the full charge capacity (FCC) of the battery.